Brainstem 2 Flashcards
2 nuclear groups related to CN 11 - spinal accessory
- brainstem portion: nucleus ambiguous
- SC portion
what makes CN 11 unique?
fibers from the SC nucleus go back up through the foramen magnum before exiting
what CNs are similar in their functional components and therefore share many of the same nuclei?
- CN 10 - Vagus
- CN 9 - glossopharyngeal
- CN 7 - Facial
4 nuclei for CN 10 and their modalities
- DMN of 10: preganglionic parasympathetic
- nucleus ambiguous: somatic motor
- solitary nucleus: VA and taste
- SNT of CN 5: somatic sensation
what is the function of the 4 nuclei used by CN 10?
- DMN of 10: visceral motor to thorax and abdomen
- ambiguous: go to contrictors of larynx and pharynx to aid in swallowing
- solitary: taste to base of tongue
- SNT of CN 5: somatic sensory from ear canal
what is a notable relationship of the 4 nuclei of CN 10?
if you put ice water in someone’s ear, you will get a vagal response of vomiting and decreased HR
4 nuclei and modalities of CN 9 - glossopharyngeal
- inferior salivatory nucleus: preganglionic parasympathetics
- nucleus ambiguous: somatic motor
- solitary nucleus: taste and VA
- SNT of CN 5: somatic sensation
what is the function of the 4 nuclei used by CN 9?
- inf. salivatory: autonomic innervation of parotid
- ambiguous: inn. larynx and pharynx w/ CN 10
- solitary: taste to posterior 1/3 of tongue
- SNT of CN 5: somatic sense form outer ear
what is an important distinction of how innervation occurs from the brainstem?
- brainstem nuclei are driven by higher centers
- w/ rare exception, everything is innervated b/l
what are the exceptions of b/l innervation?
- lower half of the facial nucleus
- accessory nucleus (he didn’t spend time on this one)
CN 8 - vestibulocochlear tracts and nuclei
- bipolar neurons from vestibular apparatus have ganglion out in temporal bone and send process to the 4 vestibular nuclei
- the lateral one becomes the vestibulospinal tract
what is another pathway that is connected with the vestibulochochlear?
MLF - median longitudinal fasciculus
MLF
-connect vestibular nuclei of CNs 6, 4, and 3 to the vestibular apparatus to control EOMs
lesion of the MLF =
dolls eyes
dorsal column / medial lemniscal pathway modalities:
- fine touch
- vibration
- pressure
- 2 pt discrimination
how can you easily ID the dorsal column pathway?
everything is on the same side until reaching the nucleus gracilis and cuneatus where the decussation occurs
lesion below the dorsal column decussation:
ipsilateral sensory loss
lesion above the dorsal column decussation
contralateral sensory loss
how is the dorsal column pathway arranged?
somatotopically
spinothalamic tract modalities
- pain
- temp
path of the spinothalamic tract
- enter at lamina 2 (sunstantia gelatinosa) and cross the anterior white commissure
- enter spinothalamic tract and ascend to VPL of thalamus
corticospinal tract
- voluntary motor
- originates at pre central gyrus and descends in cerebral peduncles, crosses in pyramidal decussation and continues down as pyramids
anatomically significant structure you would find in a cross section of the inferior pons:
- medial lemniscus
- descending spinal tract of nucleus of CN 5
- nucleus of CN 7
- 4th ventricle
- facial colliculus
- superior olivary nucleus
- group of scattered nuclei at ventral surface
what are the 3 types of descending fibers from the pre central gyrus?
- corticospinal
- corticopontine (seen in cross section)
- corticobulbar (ones that end in nuclei of brainstem like hypoglossal)
4 nuclei and their modality of CN 7 - Facial
- nucleus of CN 7 - motor
- superior salivatory: preganglionic parasympathetic
- solitary nucleus: taste, VA
- SNT of CN 5: somatic sensation
what is the function of the 4 nuclei used by CN 7?
- nucleus of CN 7: motor to muscles of facial expression
- superior salivatory: PSNS inn. of submandibular, sublingual and lacrimal glands
- solitary: taste to anterior 2/3 of tongue
- SNT of CN 5: somatic sensation of face
what is unique of the formation of CN 7 nuclei and related structures?
- the axons exit the nucleus medially and go up and around nucleus of CN 6
- this forms the facial colliculus in the floor of 4th ventricle
Bells Palsy
-lesion of facial motor nucleus or entire facial n.
a bells palsy lesions causes:
entire ipsilateral face cannot move - can’t raise eyebrows
a stroke lesion:
- will knock out lower face on contralateral side, but n. going to frontalis is b/l innervated
- CAN raise eyebrows
pop quiz:
if you have a lesion at midline of the low medulla, what will it effect?
tongue
CN 6 - abducens
reminder: LR6 SO4
- comes out of its nucleus to go inn. lateral rectus muscle
- b/l innervation
- exits brainstem at pontomedullary jxn
3 sensory parts of the trigeminal nucleus
- mesencephalic
- pontine / principal / main area
- spinal portion
*pons also holds the motor component of CN 5
mesencephalic nucleus of CN 5 is responsible for:
proprioception of face and jaw / oral cavity
pontine / principal area of CN 5 is responsible for:
touch
spinal part of CN 5 is responsible for:
pain and temp of skin of face
how to think of the different CN 5 nuclei areas:
- clinical applications
- a lesion in the medullary portion (SC portion) probably wouldn’t effect how the face percieves touch but it would effect temp
what is unique about the trigeminal ganglion?
goes to the VPM not VPL of the thalamus
another unique aspect of trigeminal ganglion
-1st order neuron for porprioception is not in the trigeminal ganglion
-it’s in the mesencephalon
=displaced ganglion
because innervation is so bilateral, when are the only 2 occasions that you lose sensation of the face?
- brainstem lesion
2. trigeminal lesion that effects the n. itself
once synapsed in the main and spinal nucleus of CN 5, efferents project collateral to where? (other than the VPM)
- facial motor nucleus
- superior salivatory nucleus
- inferior salivatory nucleus
- CN 12
- vagal parasympathetics
CN V role at the facial motor nucleus
-the opthalmic division (V1) of CN 5 goes to facial motor nucleues and bilaterally innervates the cornea
effects on blink reflex if V1 (opthalmic division of CN 5) is cut:
- touch cornea of effected side = nothing
- touch cornea of contralateral side = both eyes blink
effects on blink reflex in Bells Palsy:
- touch same side cornea: will feel pain (b/c nothing wrong w/ V1) but can’t blink (CN 7)
- touch contralateral side: will blink
CN V role at the superior salivatory nucleus
- aka lacrimal nucleus
- produce tears following corneal sensation by stimulating CN 7
CN V role at the superior AND inferior salivatory nucleus
salivation
CN V role at the CN 12
- coordinate tongue movements
- i.e: keep tongue out of the way while chewing
CN V role at Vagal parasympethics:
- pressure in mouth
- ex: vomiting from biting a piece of cartilage
structures of the mesencephalon
- ventral: cerebral peduncles
- dorsal: CNs 3 and 4 and colliculi
- cerebral aqueduct runs through it
CN 4 - trochlear
- midline so motor
- goes to inn. superior oblique (LR6 SO4)
2 unique things about CN 4
- exits the brainstem dorsally
- crosses before it exits
a lesion to CN 4 outcome:
lesion is contralateral to affected side
CN 3 - occulomotor
- in mesencephalon
- exits medially
- innervates all EOM muscles other than LR and SO
2 nuclei of CN 3
- CN 3 nucleus: somatic efferents
- edinger-westphal nucleus: pregangionic parasympathics
function of CN 3 at the edinger westphal nucleus:
contrict pupils
convergence and accomodation is performed by:
CN 3
argyll-robertson pupil
- nuerosyphilis abolishes light reflex w/o affecting accomodation
- “prostitutes pupil”
- think tabes dorsalis
substantia nigra
part of the extrapyramidal system so modulates the pyramidal system
2 parts of the substantia nigra:
- receptive part: receives info from caudate
- projection part: dopamine and Ach neurons
dopamine
inhibitory
ach
excitatory
lesion in the pyramidal system:
paralysis
lesion in extrapyramidal system:
not paralysis but motor activity will not be normal (throwing paper towels up to ceiling insted of picking it up example)
what is an example of a substantia nigra / extrapyramidal lesion that manifests in a disease?
Parkinson’s tremor
inferior colliculus
relay nucleus related to hearing
superior colliculus
- vision
- origin of tectospinal tract
- it doesn’t “see” it interprets
